Electrochemical production of phosphatic fertilizers.



- invention consisting in heating the natural or if the-aqueous solutionof same is left to duction of PhosphaticFertilizers, of which UNITED STATES PATENT OFFICE.

eronero LEVI, or ROME, ITALY.

ELECTROCHEMICAL PRODUCTION No Drawing. App1ication filed August 14,

the following is aspecification! I This invention relates to nnprovements 1n the production of phosphatic fertilizers, the

insoluble phosphates of calciun'i with fixed oxi'ds, silica and oxid of iron for instance, and also with other substances, such as fluxes and mineral coloring matter,'the heating be ing conducted in an electric furnace'until the whole of the-phosphoric anhydrid is' separated and other valuable products are obtained as fixed residues in the furnace, the former being used to make the soluble phosphatic fertilizer (which will be monocalcic phosphate); The fuine's'of the phosphoric anhydrid escaping from the electric furnace are dissolved in wate' and can be utilized either for convertingfurther quantities of natural ph-osphorite intomonocalcic phosphate, according to the method in use for the manufacture. of the double superphosphates, i

rest, under convenient conditions, it is converted into orthophosphoric acid, and this acid may then be utilized for'the production of its soluble salts, for instance'by acting either on calciumcarbonate or on lime, in the manner already known in theart, whereby industrially pure triple superphosphate or .monocalcic phosphate is obtained. Besides, phosphoric acid may combine with other bases such asammonium and potassium and thus serve as ameans for fixing them and preparing a fertilizer all the constituents of which are useful for agricultural purposes; However as hitherto phos phoric anhydrid could not be obtained sufiiciently cheaply, the processes above mentioned have never been generally used for industrial purposes;

Now according to-the present invention the preparation of the phosphoric anhydrid is rendered convenient and.- profitable by means of the electric furnace, wherein from I silica. for instance, which is very OF PHOSPHATIC FERTILIZERSi Specification of Letters Patent. Patented Feb. 21,1911.

1909. Serial No. 512,850.

1 the natural tricalcic "phosphate (phosphorite) phosphoric anhydrid can be directly obtained at a very low cost, or eventhis low cost of productioncan be de'creased still further by arranging the process in such a manner as to leave useful by products as residues in the furnace, without any notable increase in the working cost. 1 p

The .Dhosphorite is subjected in the electric furnace to'the action of a fiked oitid, ape s which, under suitable conditions, can completely displace the phosphoricanhydrid In the electric furnace the following reaction takes place: p a (2) Ca,(P0,) +3SiO =3CaSiO +P O The calcium'silicate thus formed remainsin a liquid state at the bottom of the furnace,

while the phosphoric anhydrid escapes in a gaseous condition and'can'easily be collected. Soluble silicate of sod'i'ul'n 'can be obtained as a residue instead of the silicate ciuni, by' adding to the phosphorite'and silica 'an anhydrous salt of sodi'uin, carbonate or sulfate of sodium for instance. If sulfate of sodium is used it reacts with the'silicate of calcium in the following manner (3) CaSiO5+Na SO,=Na SiO +CaSO Instead of silica, ordinary sand and any decomposable silicate such as an alkaline feldspar can be'used.

Although the reacti that it is furnished with a hood for the collection of the gaseous products, whether it be with continuous or alternatingl'cur rent, are or resistance, it is well to 0bserve't-hat, if in the reacting mass there is a reducing agent such as carbon, it may reduce the phosphoric anhydrid to' [phosphorous, a result which would be'a sheer loss of energy. It will therefore be'preferable n (21) "caii take place in any type of electric furnace, provided will be the so-called Saxony blue.

colors must be obtained in the manner. de-

scribed hereinafter the reaction shall take place in an oxidizing medium, that is in the presence of an excess of oxygen, and the carbon would therefore have a disturbing action. Further by adding to the reacting mass certain oxide or metallic salts, valuable mineral colors can he obtained. Thus, if silicic acid, oxid of'cobalt and anhydrous sodium sulfate are added to the phosphorite, the fixed residue in the furnace, after the vaporization of the phosphoric anhycirlit l,

ns enamel color is not properly speaking .a definite chemical compound. It is rather a mixture of a double silicate of sodium and calcium with oxid of cobalt, to which oer 'tain authors assign the formula ec qi) 0 instead of silica, For instance a mixture necessary. (6). On account of of phosphorite, anhydrous sulfate of sodium and iron oxid (Fe O will produce the development of the phosphoric anhydrid and leave as residue a mixture of oxids of calcium, sodium and iron; the sulfate of sodium acting in this case as'a flux.

The phosphoric anhydrid is thus obtained economically (an essential condition for competing successfully with the methods now in use for the acidification of phosphorites) for the following reasons (a). The consumption of energy is only that strictly the peculiar conditions of the process it is not necessary that the phosphorite should be very finely ground-an expensive operation, frequently essential in other methods. (0). The electrodes are burned away very slowly, since they have only to carry the current, and do not take part in the chemical reaction which (2 Finally causes the production of phosphoric anhydrid. The by-product silicate of calcium which will be ofvarying composition according to the phosphorites employed and according to the temperature attained) may be used as material for cement or for glassmaking, and will have an appreciable market value, and the soluble silicate and the mineral colors have a. still higher value. the reagent SiO by means of which the p osphoric anhydrid is freed, is

very cheap and is found almost everywhere.

' tained in the Iclaim: I 1. The

tion of p osphatic fertilizers, which comture comprising natural tricalcic phosphate, a fixed oxid capable of displacing at high temperature the phosphoric anhydrid contricalcic phosphate and in quantity sufficient to displace all of said phosphoric anhydrid,- and an anhydrous salt of sodium, and maintaining the heating of the mass until all the phosphoric anhydrid has been separated and the residue consists of molten oxid-containing material, substantially as described.

2. The process for the industrialpreparation of phosphat-ic fertilizers, which comprises heating in an electric furnace natural tricalcic phosphate mixed with silica in quantity sufiicient to displace all the phosphoric anhydrid and an anhydrous salt' of sodium, and maintaining the heating of the mass until all the phosphoric anhydrid has been separated and the-residue consists of molten soluble silicate of sodium, substantially as described.

3-. The tion of phosphatie fertilizers, which consists in heating in an electric furnace natural tricaleic phosphate, silica in suflicient quantity to displace all the phosphoric anhydrid, a salt of sodium and a coloring metallic salt, and maintaining the heating of the mass until all the phosphoric anhydrid has been separated and the residue consists of the enamel color corresponding to the salt employed, substantially as described.

process for the industrial preparaprocess for the industrial prepara- 4. The process for the industrial preparation of phosphatic fertilizers, which consists in heating in' an electric furnace natural tricalcic phosphate, silica in suflicient quantity to displace all the phosphoric anhydrid, anhydrous sodium sulfate, and 'oxid of cobalt, and maintaining the heating of the mass until all the phosphoric auhydridhas.

been separated and the residue consists of Saxony blue, substantially as described.

In witness whereof I have hereunto set my hand in presence of two witnesses.

GIORGIO LEVI.

Witnesses LE'I'IERIO LABOCOETTA, ANTONIO LABOCCE'I'IA. 

